1. Field of the Invention
The present invention relates to a thin-film magnetic head for use in a magnetic disk apparatus, a VTR, etc., and a magnetic write/read apparatus equipped with this magnetic head, and more particularly, to a very small thin-film magnetic head which has low recording magnetomotive force necessary for magnetizing a magnetic recording medium, has a fewer number of recording coil turns and has a very narrow track width, and a magnetic write/read apparatus equipped with this magnetic head.
2. Description of the Related Art
For an inductive magnetic head which has been conventionally popular, when used both for writing and reading, it is in principle advantageous to increase the number of coil turns because this provides a larger reading output. With such a magnetic head used exclusively for information writing, however, the number of coil turns can be reduced as long as the magnetomotive force required for writing is satisfied. The inductive magnetic head for exclusive use in information writing, therefore, has a simpler structure than the aforementioned inductive magnetic head designed both for writing and reading, thus facilitating the head fabrication process and improving the production yield. The magnetic head for writing only has a further advantage in easier miniaturization of the magnetic core portion and easily ensuring the high efficiency of the head.
It is a magnetic head with a single-turn coil which has the simplest structure and is attractive. It is known that the recording current needed to magnetize a magnetic recording medium using a single-turn magnetic head fabricated by the prior art design technology is around 1 A (Ampere), namely, 0.7 to 0.8 A or 1.5 A. (See E. P. Valsyn and L. F. Shew, "Performance of Single-Turn Film Heads," IEEE Trans. MAG-9, No. 3, September 1973, and W. Chynoweth, "Small Thin-film Transducers Point to Fast, Dense Storage Systems, Electronics, July 25, pp. 122-127, 1974.)
This means that the magnetomotive force of the conventional single-turn coil magnetic head does not differ from that of the conventional inductive magnetic head designed for writing and reading (several dozens of turns), which is about 1 A.multidot.T (Ampere.multidot.Turn).
Since the conventional single-turn head or few-turns head requires a recording current larger by a factor of several tens than that of the writing/reading head, the burden on the driver circuit to supply the recording current is very heavy. What is more, because of the large current, the heat generated by the coil portion will deteriorate the characteristic and reliability of the head. To cope with never stopping improvement of the density of magnetic recording apparatuses, there will be expected demands for further miniaturization of the magnetic core and further reduction of the number of coil turns. This therefore requires some design scheme for a low-magnetomotive force magnetic head, which can magnetize a magnetic recording medium with a low magnetomotive force, preferably of several dozens of milliamperes.multidot.turns (mA.multidot.T), similar to the writing current needed by the conventional inductive write/read magnetic head.
Further, since the thickness of the magnetic pole in the plane facing the recording medium for the conventional inductive magnetic head is on the order of several micrometers (.mu.m), the dimensional tolerance of machining for the pole track width has been considered to be limited to around .+-.0.5 .mu.m as long as the state-of-the-art film etching process is used, and it is very difficult to provide a narrow track width of 1 .mu.m or below. A solution to this shortcoming has been craved so far.